Variable Ground and Surface Water Response to Plant Water Use Along a Mountainous Non-Perennial Headwater Stream Under Severe Drought Conditions
Abstract
Many streams show daily fluctuations of water levels, impacting downstream water quality and availability. In perennial systems, these cycles are often attributed to snowmelt influxes and losses due to evapotranspiration. Despite observed diel drying patterns in intermittent reaches, there is limited work that explores how water losses from plant water use impact streamflow and shallow groundwater dynamics in non-perennial streams during recession and stream drying. As more streams begin to dry under intensifying drought conditions, it is important to accurately characterize the underlying causes of stream drying to inform sustainable water and critical habitat management decisions. The goal of this study is to investigate how the magnitude and timing of plant water use, as measured by native riparian sap flow, influences stream drying and groundwater dynamics along a headwater stream corridor. We hypothesized that shallow groundwater losses driven by plant water use largely control the timing and duration of stream drying. To test this, we installed sap flow, soil moisture, and photosynthetically active radiation (PAR) sensors, as well as three sets of riparian and in-stream nested piezometers at three focal transects along the north fork of Gibson Jack Creek, Idaho, a headwater stream observed to exhibit a wide range of flow permanence. Our initial results show a variable and weak relationship between the timing and magnitude of sap flow and ground and stream water levels. Under ongoing severe drought conditions, we propose that catchment-scale water availability is the primary driver of plant water use, since even riparian trees have become water-limited, overriding potential local-scale controls on non-perennial flow in headwater streams.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H45P1357N